This invention generally relates to medical instruments and methods for retrieving material from within a body. More particularly, the invention relates to retrieval methods, devices, and compositions for stabilizing and removing stones such as urinary tract stones, gall stones, and other objects found in the body.
Medical retrieval devices generally are used to retrieve biological and foreign material, such as kidney stones and other calculi, from the body of a patient. Such medical retrieval devices may be used through an endoscope or a laparoscope. The use of such devices to capture foreign material like stones is made difficult by the freedom of movement of the stones within the body. A stone may dislodge from its resting place when contacted with a retrieval device. This may cause the stone to move into an area of the body that renders the stone inaccessible or undetectable thus preventing the capture and removal of the stone.
Larger stones often need to be shattered because their size prohibits non-surgical removal from the body. Shattering a stone (by, for example, light, chemical, or physical energy) will disperse the resulting stone fragments from the original location of the stone. Stone fragments that are not removed from the body can form the nuclei for the formation of new stones. The dispersal of the fragments caused by the shattering process can cause fragments to move into inaccessible or unknown areas of the body thus preventing or interfering with the capture and removal of the fragments.
It is an object of the invention to facilitate the capture and removal of objects located within the body. The invention generally includes the use of a material that exists in liquid form at temperatures below about body temperature and as a gel at temperatures about at and above body temperature. The temperature at which the transition from liquid to gel occurs is referred to as the lower critical solution temperature (LCST), and it can be a small temperature range as opposed to a specific temperature. Materials appropriate for use according to the invention possess a LCST and are referred to as LCST materials. The methods and systems of the present invention generally involve the injection of an LCST material into a cavity or space within the body. Once inside the body, the LCST material can contact and at least partially contain an object. In many cases, the LCST will entirely envelope and surround the object. As the temperature of the LCST material rises due to the internal temperature of the body, the LCST material will reach its LCST and thus transition into the gel phase. (The specific transition point or range is determined by the specific LCST material utilized.) An object in contact with the LCST material thus will be at least partially trapped and stabilized by the gel. The stabilization of the object allows for easier capture and retrieval of the object. Stabilization of the object also allows for easier use of a lithotripsy device for fragmenting the object because the gel holds the object in place. Furthermore, the gel prevents the free dispersal of fragments of the object after the object is broken apart by the lithotripsy device. Preventing the dispersal of the fragments allows for easier capture and retrieval of the object fragments.
The invention, in one aspect, includes a method of stabilizing an object in the body of a patient. The method includes injecting a lower critical solution temperature material in a flowable form into the body of the patient to contact the object. The method further includes allowing the lower critical solution temperature material to form a gel in the body due to a temperature inside the body. The object thus is contained at least partially within the gel and stabilized by the gel.
In one embodiment according to this aspect of the invention, the method involves the use of the lower critical solution temperature (LCST) material which remains in the flowable form below about the temperature inside the body of the patient. The LCST material can form the gel about at and above the temperature inside the body of the patient.
In other embodiments, the method can include retrieving the stabilized object from the gel and/or breaking the object into at least two fragments. At least some of the fragments remain at least partially within the gel and stabilized by the gel, and these fragments can then be retrieved from the gel.
In another aspect, the invention relates to a system for stabilizing an object in the body of a patient. The system includes a lower critical solution temperature material which remains in a flowable form below about a temperature inside the body of the patient and which forms a gel about at and above the temperature inside the body of the patient. The system also includes a catheter for transferring the lower critical solution temperature material into the body in the flowable form and a guide wire for introducing the catheter into the body and guiding it to about the location of the object. The system also includes a mechanism to force the lower critical solution temperature material in the flowable form through the catheter and into the body to contact the object. The lower critical solution temperature material gels inside the body due to the temperature inside the body and thereby contains at least a portion of the object within the gel to stabilize the object.
One embodiment according to this aspect of the invention involves the use of the catheter to remove the lower critical solution temperature material from the body.
In still another aspect, the invention features a system for stabilizing an object in the body of a patient. The system includes a lower critical solution temperature material which remains in a flowable form below about a temperature inside the body of the patient and which forms a gel about at and above the temperature inside the body of the patient. The system also includes a percutaneous access device for transferring the lower critical solution temperature material into the body in the flowable form. The system further includes a mechanism to force the lower critical solution temperature material in the flowable form through the percutaneous access device and into the body to contact the object. As before the lower critical solution temperature material gels once inside the body due to the temperature inside the body and thereby contains at least a portion of the object within the gel to stabilize the object.
In one embodiment according this aspect of the invention, the percutaneous access device comprises a needle. In some embodiments, the system further includes a catheter for removing the lower critical solution temperature material from the body.
In some embodiments of this and the prior aspects of the invention, the mechanism used to force the lower critical solution temperature material into the body comprises a syringe.
The lower critical solution temperature material used in connection with all aspects of the invention can comprise a block copolymer with reverse thermal gelation properties. The block copolymer can further comprise a polyoxyethylene-polyoxypropylene block copolymer such as a biodegradable, biocompatible copolymer of polyethylene oxide and polypropylene oxide. The molecular weight of the block copolymer can be, for example, between 5,000 and 25,000, and more particularly between 7,000 and 15,000.
Also, the lower critical solution temperature material can include a therapeutic agent such as an anti-angiogenic agent.
The foregoing and other objects, aspects, features, and advantages of the invention will become more apparent from the following description and from the claims.